The present invention relates to a digital signal detecting apparatus, and more particularly to a digital signal detecting apparatus for reproducing high-density digital signals which are recorded on a recording medium in systems for processing digital signals such as digital videotape recorders (VTR).
The schematic diagram for a conventional digital signal detecting apparatus is shown in FIG. 1. In FIG. 1, a reproducing head 2 transforms a magnetic digital signal which is recorded on magnetic tape 1 into an electric signal and inputs this data signal into a reproducing amplifier 3. The data signal, which is deteriorated during amplification in the reproducing amplifier, is compensated in an equalizer 4 and sent to the non inverting terminal (+) of a comparator CP constituting part of a comparison unit 5.
Also, a comparison reference voltage VR is applied to the inverting terminal (-) of the comparator CP.
The compared value obtained by comparing the data signal with the comparing reference voltage VR which are applied to the inverting (-) and noninverting (+) terminals of the comparator CP is fed from the output terminal of the comparator CP to the PLL 6 and the data detector unit 7, respectively.
Here, the PLL 6 is used to reproduce the clock signal by utilizing the compared value outputted from the comparator 5 and to transfer the reproduced clock signal to the data detector 7 and the demodulator 8.
The data detector 7 detects a synchronous signal by utilizing the compared value of the comparator 5 and the clock signal of the PLL 6 and sends it to the demodulator 8. Therefore, the demodulator 8 acts to demodulate the modulated digital data signal from the synchronous signal and the clock signal and sends it to the output terminal OUT.
However, the conventional digital signal detecting apparatus as mentioned above has problems in that the differential characteristics and random signal characteristics in high-density data signals recorded on recording media are deteriorated.